Single-lobe surface-emitting quantum cascade laser with 2nd-order metal-semiconductor gratings

Grating-coupled, surface-emitting (GCSE) quantum-cascade lasers (QCLs) have been studied since 2000 [1] and generally operate in a two-lobe beam pattern [1,2]. Recently, single-lobe surface emission has been reported either from asymmetrically-coated devices [3] or from chirped-grating, ring-cavity devices [4], but at powers ≤ 0.1 W. Here we present the implementation of a novel concept for high-power, single-lobe surface emission, which employs metal-semiconductor, 2nd-order distributed feedback (DFB) gratings [5]. Initial devices demonstrate ~ 0.4 W single-lobe, single-mode power from 4.75 μm-emitting GCSE QCLs.